SYNOPSIS Potentiation of venospastic action of 5‐HT by methysergide and ergotamine was demonstrated in man by using venomotor receptors as substrate in a venoconstriction test. 5‐HT facilitation was observed only when anti‐migraineous drugs were tested in concentrations similar to those expected after therapeutic administration. When ergotamine and methysergide were used in higher concentrations, the expected antagonism to 5‐HT was clearly demonstrated. It is concluded that methysergide and ergotamine therapy is not antiserotonergic. These drugs act as partial agonists of 5‐HT. Methysergide and ergotamine facilitation of 5‐HT activity may occur at peripheral vasomotor receptors, or centrally in the brain. This latter probably is consistent with the postulated central nature of pain in essential headache.
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Fanciullacci et al. (1976) studied this question.